The second of Saturday morning's free practice sessions in Monaco was interrupted by a violent accident for Jenson Button, which left the young Briton requiring urgent medical attention.

Having starred in Thursday's opening qualifying session, and gone well in the first part of Saturday's practice, the BAR-Honda was being tipped for another strong performance in Sunday's grand prix, but that now appears to have been put aside after he was carefully extracted from what remained of his car following a brutal accident exiting the tunnel section of the street circuit.

According to initial reports, the BAR made contact with the barrier as Button exited the tunnel, before turning sharply across the track and hitting the retaining wall at barely unabated speed. There was little movement in the cockpit, and Button was immediately attended by the medical team.

Further news will follow as it emerges....